Ask an Expert: LED Traffic Lights

Each year, more than 4 million traffic lights consume an estimated 3 billion kilowatt-hours of electricity. Switching to energy-efficient LED lamps trims municipal budgets and lowers energy use nationwide. More than 50 percent of all traffic signals have been converted to LEDs in the U.S.

A light emitting diode is a tiny semiconductor that emits visible light when an electric current passes through it. Unlike ordinary incandescent bulbs, there is no filament. LED traffic signals use high-brightness LEDs connected together to build a cluster consisting of hundreds of LEDs.

LED lights only produce light in the desired colors, such as red, yellow or green, making them ideal for traffic signals. There is no need to filter the light through a lens. As a result, true colors are produced more efficiently, with minimal waste of heat energy. LED lights consume only 10 percent of the energy used by incandescent lamps (10-25 watts versus up to 150 watts, respectively). LED lights also look brighter since the light is distributed equally across the entire surface (an advantage in poor weather conditions).

LED lamps last 100,000 hours (fifty times longer than incandescent bulbs at 2,000 hours) because there are no filaments to burn out. Relamping cycles and emergency replacement projects decrease, reducing maintenance costs. This provides staff with more time for other projects.

LED lights also increase traffic safety as they minimize the number of signal outages and due to their low energy consumption, LEDs are more economical to use with battery back-up systems. Batteries can keep LED traffic signals functioning for up to 24 hours in the event of a power outage.